IPv6 over the TSCH mode of IEEE 802.15.4e
|The information below is for an older proposed charter
IPv6 over the TSCH mode of IEEE 802.15.4e WG
||IPv6 over the TSCH mode of IEEE 802.15.4e
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6TiSCH: "IPv6 over the TSCH mode of IEEE 802.15.4e".
Low-power and Lossy Networks (LLNs) interconnect a possibly large number
of resource-constrained nodes to form a wireless mesh network. The
6LoWPAN, ROLL and CoRE IETF Working Groups have defined protocols at
various layers of the protocol stack, including an IPv6 adaptation
layer, a routing protocol and a web transfer protocol. This protocol
stack has been used with IEEE802.15.4 low-power radios.
The Timeslotted Channel Hopping (TSCH) mode was introduced in 2012 as an
amendment to the Medium Access Control (MAC) portion of the IEEE802.15.4
standard. TSCH is the emerging standard for industrial automation and
process control LLNs, with a direct inheritance from WirelessHART and
ISA100.11a. Defining IPv6 over TSCH, 6TiSCH is a key to enable the
further adoption of IPv6 in industrial standards and the convergence of
Operational Technology (OT) with Information Technology (IT).
The nodes in a IEEE802.15.4 TSCH network communicate by following a
Time Division Multiple Access (TDMA) schedule. A timeslot in this
schedule provides a unit of bandwidth that is allocated for
communication between neighbor nodes. The allocation can be programmed
such that the predictable transmission pattern matches the traffic. This
avoids idle listening, and extends battery lifetime for constrained
nodes. Channel-hopping improves reliability in the presence of narrow-
band interference and multi-path fading.
These techniques enable a new range of use cases for LLNs, including:
- Control loops in a wireless process control network, in which high
reliability and a fully deterministic behavior are required.
- Service Provider networks transporting data from different independent
clients, and for which an operator needs flow isolation and traffic
- Networks comprising energy harvesting nodes, which require an
extremely low and predictable average power consumption.
IEEE802.15.4 only defines the link-layer mechanisms. It does not define
how the network communication schedule is built and matched to the
traffic requirements of the network.
Description of Working Group:
The Working Group will focus on enabling IPv6 over the TSCH mode of the
IEEE802.15.4 standard. The extent of the problem space for the WG is
one or more LLNs, possibly federated through a common backbone link
via one or more LLN Border Routers (LBRs). The WG will rely on, and if
necessary extend, existing mechanisms for authenticating LBRs.
Initially, the WG has limited its scope to distributed routing over a
static schedule using the Routing Protocol for LLNs (RPL) on the resulting
network. This new charter allows for the dynamic allocation of cells and
their exchange between adjacent peers to accommodate the available bandwidth
to the variations of throughput in IP traffic.
The WG will continue working on securing the join process and making that fit
within the constraints of high latency, low throughput and small frame sizes
that characterize IEEE802.15.4 TSCH.
Additionally, IEEE802.15.4 TSCH being a deterministic MAC, it is envisioned
that 6TiSCH will benefit from the work of DetNet WG to establish the so-called
deterministic tracks. The group will define the objects and methods that need
to be configured, and provide the associated requirements to DetNet.
The WG will interface with other appropriate groups in the IETF
Internet, Operations and Management, Routing and Security areas.
The group will:
- Produce a specification of the 6top sublayer that describes the protocol for
neighbor nodes to negotiate adding/removing cells. This work will leverage
cross participation from IEEE members including the IEEE 6TiSCH Interest Group
(IG 6T) to define protocol elements and associated frame formats.
- Produce a specification for a default 6top Scheduling Function including the
policy to enable distributed dynamic scheduling of timeslots for IP traffic.
This may include the capability for nodes to appropriate chunks of the
matrix without starving, or interfering with other 6TiSCH nodes. This
particular work will focus on IP traffic since the work on tracks is not yet
advanced enough to specify their requirements.
- Produce requirements to the DetNet WG, detailing 6TiSCH chunks and tracks,
and the data models to manipulate them from an external controller such
as a PCE.
- Produce a specification for a secure 6TiSCH network bootstrap, adapted
to the constraints of 6TiSCH nodes and leveraging existing art when possible.
- Keep updating the "6TiSCH architecture" that describes the design of 6TiSCH
networks. This document highlights the different architectural
blocks, signaling and data flows, including the operation of the network in
the presence of multiple LBRs. The existing document will be augmented
to cover dynamic scheduling and application of the DetNet work but will not
be delivered within this round of chartering.
- Produce a YANG Data Model to manage the 6top sublayer. A mapping to an
existing protocol (such as Concise Binary Object Representation (CBOR) over the
Constrained Application Protocol (CoAP)) will be provided. This work depends on
the standardization of a method to access management data resources in
constrained devices, such as proposed by CoMI (CoAP Management Interface) or
COOL (Constrained Objects Language).
Non-milestone work items:
The Working Group regularly organizes interoperability events with support from
ETSI (i.e., ETSI 6TiSCH Plugtests) to get feedback from implementers early on
in the standardization process, and produce better standards.